#include <iterator>
#include <list>
#include <iostream>
using namespace std;

void print(list<int> input){
        cout << "list now: " << endl;
        for (auto i : input){
            cout << i <<" ";
        }
        cout << endl;
    }

int main(){
    list<int> input = {1,4,3,2,2,1,9};

    auto it1 = input.begin();
    auto it2 = input.begin();
    advance(it2, 1);

    for(; it2 != input.end(); it2++, it1++){
        cout<<"it1, it2: "<< *it1<<","<<*it2<<endl;
    }

    return 0;
}